Cabazitaxel, 4-acetoxy-2α-benzoyloxy-5β,20-epoxy-1-hydroxy-7β,10β-dimethoxy-9-oxo-11-taxadiene-13α-yl(2R,3S)-3-tert-butoxycarbonylamino-2-hydroxy-3-phenyl-propionate, has the structure as represented by formula (I):

Cabazitaxel is a semi-synthetic taxoid small molecule compound developed by Sanofi-aventis, France. It is a second line treatment for prostate cancer and is approved to be marketed in America in June, 2010.
Cabazitaxel has similar anti-cancer mechanism and feature with docetaxel, both are anti-microtubule drugs. The binding of Cabazitaxel to tubulin promotes the assembly of tubulin into microtubules and simultaneously inhibits disassembly, and thereby stabilizing microtubule dynamics, and in turn, blocking mitosis and interphase cellular functions. Cabazitaxel is used for a patient with advanced prostate cancer who does not respond to docetaxel and even with worsened condition. It is a leading choice for the treatment of advanced, hormone-refractory prostate cancer. Cabazitaxel injection solution is used in combination with prednisone for treatment of patients with metastatic hormone-refractory prostate cancer (mHRPC) previously treated with a docetaxel-containing regimen.
Crystalline form is one of the influential factors that affect the quality, therapeutic efficacy and processing property of a medicine. Polymorphism refers to the occurrence of two or more types of molecular conformation of a same compound by controlling the formation condition, and thereby forming different solid crystalline forms. Polymorphism, which is common in the development of a medicine, is an influential factor for the quality of a pharmaceutical product. Different crystalline forms of a same compound exhibit the same composition, but different crystalline microscopic structures. Thus, polymorphs of a compound can differ in morphologic appearance, physicochemical properties and biological activity. These properties directly influence processing property, stability, solubility and bioavailability, and in turn, quality, safety, efficacy and application of a medicine. Therefore, there is a need to comprehensively consider the polymorphism issue in the development of a pharmaceutical product.
Currently, Cabazitaxel is known to give rise to a variety of crystalline forms. Patent WO2005/028462 identifies and characterizes a crystalline form A of Cabazitaxel, i.e., the acetone solvate of 4-acetoxy-2α-benzoyloxy-5β,20-epoxy-1-hydroxy-7β,10β-dimethoxy-9-oxo-11-taxadiene-13α-yl(2R,3S)-3-tert-butoxycarbonylamino-2-hydroxy-3-phenylpropionate. Patent WO2009/115655 identifies and characterizes anhydrate forms B, C, D, E and F, ethanolate forms B, D and E, ethanol/water hetero-solvate F, monohydrate form C and dihydrate form C of Cabazitaxel.